Mo. Rev. Stat. § 292.480
That all scaffolds, hoists, stays, ladders, supports, or other mechanical contrivances, erected or constructed by any person, firm or corporation, in this state, for the use in the erection, repairing, alteration, painting, tuckpointing, removal or any work whatsoever of any house, building, bridge, viaduct, or other structure, shall be erected and constructed, in a safe, suitable and proper manner, and shall be so erected and constructed, placed and operated, as to give proper and adequate protection to the life and limb of any person or persons, employed or engaged thereof, or passing under or by the same, and in such manner as to prevent the falling of any material that may be used or deposited thereon. Scaffolding or staging, swung or suspended from an overhead support, more than twenty feet from the ground or floor, shall have where practicable a safety rail properly bolted, secured and braced rising at least thirty-four inches above the floor, or main portion of such scaffolding or staging, and extending along the entire length of the outside and ends thereof, and properly attached thereto, and such scaffolding or staging shall be so fastened as to prevent the same from swaying from the building or structure.
§ 292.480, RSMo